6505 ReTube - Preamp Layout/Tube Positions? Help!

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SPage666
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Joined: Sun Jan 03, 2021 1:15 am

6505 ReTube - Preamp Layout/Tube Positions? Help!

Post by SPage666 » Sun Jan 03, 2021 1:33 am

Hi all!

I'm in the process of ordering new tubes for my 6505 head. She's been out of action for some time and needing some love.

I'm not here to ask what are the best tubes for my amp - I understand that's inherently subjective.

Rather, what I'm hoping someone could advise is the configuration for the preamp section i.e "left to right V1 input, V2 phase etc"
I've recently stumbled upon advice warning against putting a Tung Sol 12AX7 in a 'cathode follower' position - whatever the hell that means. Essentially what was said was that Tung Sol's aren't well suited to these positions and will die young. Any truth or further insight? I'm definitely going to run one or two Balanced Tung Sol's in my amp because I think they're great, but I'm wondering where they shouldn't go?

Also, I'm 99.5% sure, but 2009 Peavey 6505 head - NOT bias adjustable right? Just plug and play?

Any help would be greatly appreciated. Thanks.

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Enzo
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Re: 6505 ReTube - Preamp Layout/Tube Positions? Help!

Post by Enzo » Mon Jan 04, 2021 1:38 pm

The 5150/6505 has no bias adjustment.

We have discussed this multiple times here.

The V numbers refer to the schematic, NOT the order of tubes on the chassis. Although in many amps they are the same. The small tubes are numbered from the end of the chassis: V 1-2-5-3-4.

V1,2,5 are all stages in the preamp. V1 handles the input stage.

V3b is the driver for the FX loop, and it is a cathode follower. V3a is the return for the FX loop and is a normal gain stage.

V4 is your phase inverter, and it is sorta like a cathode follower, but does not put as much voltage on the cathodes

CAthode follower stages put a relatively high voltage on the cathode, which is just right next to the heater, and the voltage can break down in some tubes.

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